Localization and expression of putative circadian clock transcripts in the brain of the nudibranch Melibe leonina

Abstract

The nudibranch, Melibe leonina, expresses a circadian rhythm of locomotion, and we recently determined the sequences of multiple circadian clock transcripts that may play a role in controlling these daily patterns of behavior. In this study, we used these genomic data to help us: 1) identify putative clock neurons using fluorescent in situ hybridization (FISH); and 2) determine if there is a daily rhythm of expression of clock transcripts in the M. leonina brain, using quantitative PCR. FISH indicated the presence of the clock-related transcripts clock, period, and photoreceptive and non-photoreceptive cryptochrome (pcry and npcry, respectively) in two bilateral neurons in each cerebropleural ganglion and a group of <10 neurons in the anterolateral region of each pedal ganglion. Double-label experiments confirmed colocalization of all four clock transcripts with each other. Quantitative PCR demonstrated that the genes clock, period, pcry and npcry exhibited significant differences in expression levels over 24 h. These data suggest that the putative circadian clock network in M. leonina consists of a small number of identifiable neurons that express circadian genes with a daily rhythm.

Diversity of Light Sensing Molecules and Their Expression During the Embryogenesis of the Cuttlefish (Sepia officinalis)

“…In our phylogenetic analysis ( Figure 4 ), we found three main monophyletic groups. One of the cryptochrome sequence of S. officinalis is grouped with other molluscan sequences, together with Euprymna scolopes escry2 ( Heath-Heckman et al, 2013 ) and the nudibranch Melibe leonina non-photoreceptive cryptochrome ( Duback et al, 2018 ). This molluscan clade is part of a larger protostomian monophyletic group (PP = 1; BS = 89) and an even larger bilaterian monophyletic group (PP = 1; BS = 98) gathering all the CRY 1 , CRY 2 and CRY 3 sequences of our analysis.…”

“…As there is a small expression of Sof_CRY 6 in the brain of the juvenile this might mean that the expression start in very advanced stage 30 embryos as the one we used for in situ hybridization was very close to hatching. We cannot rule out the fact that this difference of expression might be due to a pattern of daily cycling of the gene as the expression of cryptochromes is known to oscillate during the day (in nudibranchs: Duback et al, 2018 ; in Crustacea: Biscontin et al, 2019 ).…”

Differential Impacts of the Head on Platynereis dumerilii Peripheral Circadian Rhythms

“…Molecular data on rhythms and clocks in marine invertebrates have become increasingly available over the last decade, now including the bivalves Mytilus californianus (Connor and Gracey, 2011) and Crassostrea gigas (Perrigault and Tran, 2017), the sea slugs Hermissenda crassicornis , Melibe leonina , and Tritonia diomedea (Cook et al, 2018; Duback et al, 2018), the isopod Eurydice pulchra (Wilcockson et al, 2011; Zhang et al, 2013; O’Neill et al, 2015), the amphipod Talitrus saltator (Hoelters et al, 2016), the lobsters Nephrops norvegicus (Sbragaglia et al, 2015) and Homarus americanus (Christie et al, 2018), the mangrove cricket Apteronemobius asahinai (Takekata et al, 2012), the copepods Calanus finmarchicus (Häfker et al, 2017), and Tigriopus californicus (Nesbit and Christie, 2014), the Antarctic krill Euphausia superba (Mazzotta et al, 2010; Teschke et al, 2011; Pittà et al, 2013; Biscontin et al, 2017), the Northern krill Meganyctiphanes norvegica (Christie et al, 2018), the marine midge C. marinus (Kaiser and Heckel, 2012; Kaiser et al, 2016), and the marine polychaete P. dumerilii (Zantke et al, 2013; Schenk et al, 2019). On the marine vertebrate side, especially teleost fish species have been investigated (Park et al, 2007; Sánchez et al, 2010; Hur et al, 2011; Watanabe et al, 2012; Vera et al, 2013; Rhee et al, 2014; Toda et al, 2014; Mogi et al, 2015; Okano et al, 2017).…”

Influence of light and temperature cycles on the expression of circadian clock genes in the mussel Mytilus edulis

“…Despite the importance of clock genes in regulating endogenous rhythmic processes in diverse phyla, the molecular mechanisms governing timekeeping ability are an understudied aspect of molluscan ecology. Recently emerging studies have characterised clock genes in gastropods (Cook et al, 2018;Duback et al, 2018;Schnytzer et al, 2018;Bao et al, 2017;Constance et al, 2002), cephalopods (Heath-Heckman et al, 2013), and bivalves Sun et al, 2016;Pairett & Serb, 2013) including mussels (Chapman et al, 2017;Connor & Gracey, 2011). Blue mussels, Mytilus edulis, are an edible species of commercial importance (FAO, 2018), a biogenic keystone species (Gutiérrez et al, 2003) and are considered early indicators of the effects of climate change (Zippay and Helmuth, 2012).…”